Heat from a safe high energy density fuel, such as aluminum, is used to generate electrical power. In some applications, the fuel may use seawater as an oxidizer. Additionally, the hybrid power system uses a highly efficient and silent thermoacoustic power converter (TAPC) to convert the thermal energy from the oxidation of aluminum to AC electrical energy. The AC electrical energy is converted to DC energy and stored in a battery. In situations demanding low power, the battery can provide power while the fuel combustion process is suspended.

A cryocooler may comprise a first stage, a second stage and a phase control device. The first stage may define a first volume. The second stage may define a second volume. The phase control device may be positioned between the first stage and the second stage to receive a flow of working fluid between the first stage and the second stage. The phase control device may comprise a flange and a plunger. The flange may be positioned along a longitudinal axis parallel a direction of the working fluid flow. The plunger may be translatable along the longitudinal axis at least partially within the flange. The plunger and the flange may be sized such that the plunger and the flange define a gap there between and a dimension of the gap is determined by a position of the plunger along the longitudinal axis.

Heat from a safe high energy density fuel, such as aluminum, is used to generate electrical power. In some applications, the fuel may use seawater as an oxidizer. Additionally, the hybrid power system uses a highly efficient and silent thermoacoustic power converter (TAPC) to convert the thermal energy from the oxidation of aluminum to AC electrical energy. The AC electrical energy is converted to DC energy and stored in a battery. In situations demanding low power, the battery can provide power while the fuel combustion process is suspended.